I've done work for a fair number of banks and insurance companies, and my anecdotal impression is that there is always a java system siphoning data from the cob

I've done work for a fair number of banks and insurance companies, and my anecdotal impression is that there is always a java system siphoning data from the cobol systems... Both stay around for the same reason: backwards compatability and a stable api+abi. If you find and old Java system it's often trivial to do changes and recompile. Even a few years old C program is often problematic due to changes in the OS or libraries. I have no idea if it's possible to compile a couple of years old js code...